a / ac

a before a consonant (including h): bara a menyn (bread and butter), mam a dad (mum and dad), haul a glaw (sun and rain).

ac before a vowel: afal ac oren, Caerdydd ac Abertawe, Siân ac Aled.

ac before some common words that start with a consonant: forms of bod such as mae, roedd and bydd, and mewn, fel and felly: ac mae hi'n braf, ac roedd e'n hwyr. This goes back to older Welsh, where mae was y mae and began with a vowel.

The aspirate mutation. After a, the letters c, p and t change: c → ch, p → ph, t → th. te a choffi (tea and coffee), halen a phupur (salt and pepper), cig a thatws (meat and potatoes). Other letters stay the same: bara a menyn. See aspirate mutation.

This change is standard in writing and careful speech. In relaxed everyday speech many people leave it out and say te a coffi; both are heard.

And the: a + y = a'r: y ci a'r gath (the dog and the cat). See The Article: Y, Yr and 'r. Do not mix up a (and) with â (with), which has a to bach; see â gyda tua na + aspirate mutation.